Validação de antissoro para uso em imuno-histoquímica para detecção de Trypanosoma cruzi

Abstract

Introduction: The diagnosis of T.cruzi infection is essential in many situations, especially in cases of reinfection in individuals with cardiac transplants. Its diagnosis can be confirmed by finding T. cruzi nests in different samples, such as the endomyocardial biopsy (EMB) to evaluate graft rejection. Because they are scarce, such nests are not always identified routinely. To increase the sensitivity of this diagnosis, immunohistochemistry (IHC) may be promising. Objective: To test an antiserum for detecting T. cruzi in histological sections by IHC. Methods: We used: 1) positive controls (PC): 13 EMB, 12 skin biopsies and 1 heart withT. cruzi nests in sections stained with hematoxylin-eosin (HE); 2) negative controls: a) 10 explanted hearts and 10 EMB without amastigotes nests nor clinical or laboratory signs of chagasic infection; b) 5 skin biopsies and 1 intestinal biopsy with leishmaniasis; 3) Cases:31 EMB of chagasic patients without parasite nests in HE sections and positive by PCR for T. cruzi DNA. As a primary antibody in IHC, hyperimmune serum from T.cruzi-infected rabbits was used. Results: IHC was positive in 21 of the 26 PC (80,8%) and in 1 case of cutaneous leishmaniasis. Sensitivity, specificity, positive predictive value and negative predictive value were, respectively, 80.8%, 96.2%, 95.5% and 83.3%. In 4 of the 31 cases (12.9%), IHC revealed T. cruzi nests not recognized by conventional histological examination. Conclusions:The results of the study show that IHC using the tested antiserum increases the sensitivity of the diagnosis and recommend its routine use in the evaluation of EMB of cardiac transplanted patients with Chagas' disease.